troubleshoot: how do I spec a resistor to test as proxy load?

[riotubes]

I could really use some help. Having difficulty isolating the problem with a a current build. The project is an output stage for a dac. I could use your feedback on identifying the culprit: (a) transformer, (b) HV regulator or (c) output stage. The output stage requires a 70V HV supply, a -5V supply and runs at 33mA and should drop about 33ish VDC across the IV resistor. My problem is that under load, the output of the HV reg is 50V (not 70V) and I measure 16V instead of 35V spec'd at the critical spot on the output stage. The HV reg meausures 70V no prob when not connected. I have built multiple HV regs thinking this is where the problem is. I now think it is the output stage or transformer. With the above specs can I use a resistor as a dummy load to test the transformer? If so, what would be the specs of this resistor dummy load?